Apparatus for the production of dense foam



Dec. 3, 1929. THOMSON V 1,737,624

APPARATUS FOR THE PRODUCTION OF DENSE FOAM Original Filed Dec. 20, 1926 Fig.2.

GEORGE MILLER THdMsoN.

INVENTO y ATTORNEY.

ture be homogeneous throughout, that is, that Patented Dec. 3, 1929 UNITED STATES,

PATENT OFFICE GEORGE m. 'rrromsorr, or CALEDONIA, ONTARIO, CANADAJWSiIGNOR TO cannon G scum!) ALABASTINE COMPANY, LIMITED, or rams, ONTARIO, CANADA APPARATUS FOR THE PRODUCTION OF DENSE FOAM.

Original application filed December 20, 1926, Serial No. 156,059, and in Canada February 22, 1827. Divided and this application filed March 18, 1927. "Serial No. 176,560.

10 films of water to form bubbles, which accumulate in a mass of foam. In attempting, however, to produce a dense, homogeneous foam suitable for commercial use in the arts, unexpected difliculties were encountered 15 and this invention is designed to overcome such difficulties and to produce in a simple, economical manner a foam well adapted to meet allthe re uirements of the arts.

The object o the invention is thus to ro- 2Q vide a simple process and apparatus W ich ma be operated continuously or periodical y, as desired, to produce a homogeneous foam of any required density and having sufficient body to make it capable of withstanding the usage incident to its being formed into, or incorporated in, industrial roducts. Obviously such a foam must be so ormed that the film surrounding the individual volumesof air will not be readily ruptured, that its density may be regulated in accordance with the specific requirements of the use to which it is to be applied and that the bubbles of which it is formed will be sub-' stantially uniform in size. Furthermore, in order that the foam may meet the requirements of the Specific use to which it is to be applied, the process and apparatus for I producing it must be subject to such control that the several characteristics required of 7 the foam may be readily" imparted to it by regulation of the operation of theprocess and apparatus.

For example, in the production of cellular building materials, such as wall-board or blocks, it is desirable that the cellular structhe size of the pores be substantially uniform and that they be uniformly distributed throughout the mass. In order that this uniformity in the material may be obtained,

in which the regulated in accordance with the weight desired in the finished material. This invention however is directed to the production of the foam itself and not to the manner of using it.

Briefly stated the invention resides in a processand apparatus for the production of foam comprising passing air in regulated volumes into colloidized water and reducing the size of the bubbles formed in accordance with the density duced.

The invention will now be described in detail, reference being made to the accompanying drawing, which illustrates by way of example one form of apparatus for operat-' in the process and in which ,igure 1 is a sectional elevation, Figure 2 is a plan view of the apparatus shown in Figure 1, p

Figure 3 is a fragmentary View of one of each set of vertical arms with additional agitating blades secured thereto.

required in the foam pro- The tank or chamber 1 has a perforated plate 2 located above its bottom and a discharge spout 3 near its top. The valve-controlled pipe 4 conducts suitably colloidized water from a source of supply and discharges the same into the tank immediately above the perforated plate. The pipe 4 is preferably connected with a water chamber containing a float-controlled valve 14:. The pipe 5 havmg a valve 6 is connected to a source of air A ressure may be controlled as desired, and dlscharges into the zone beneath the perforated plate in the tank 1. The shaft has secured to its lower end one or more horizontal arms 10, provided with vertical arms 11 and the hollow shaft 8 which surrounds shaft 7 carries one or more horizontal arms 9 which are likewise provided with downwardly projecting vertical arms 12.

ulation of valve 6, into the space in the tank of supply,

arm is tapered to a relatively sharp edge at the rear, as illustrated, particularly m Figure 2, for reasons to be describ'ed'later.

The operation of the invention will now be described as follows:

Golloidized water, that is, water to which a colloid such as saponin, organic acids, aldehydes, sugar, etc, is added in the quantity required to impart a desired surface tenslon to the bubbles to be formed, is caused to flow into the tank 1 through pipe 4 until a depth of several inches, say three to five, of colloidized water rests upon the perforated plate 2. At the same time air from a suitable source under substantially constant pressure. is caused to flow through pipe 5, by regbclow the perforated plate, through which it passes in fine streams and enters the collo1dized water. Bubbles thus form in and rise to the surface of the water, where they accumulate in the form of a light foam, the bubbles being relatively large and substantlally uniform in size. v

The size of the bubbles formed depends on the size of the perforations in the plate 2 and the velocity of the air admitted through such holes. The smaller the perforations for a fixed air velocity, the smaller will be the bubbles formed. Likewise the less the velocity agitating or cutting action of air for perforations of constant diameter, the smaller will be the bubbles formed.

When the light foam thus formed rises to a point where it is engaged by the stirrin or agitating device carried by the shafts and 8, the bubbles are reduced in size to form a foam of the required density b therepeated agitating or cutting action 0 the arms 11, 12 and 14. As the foam rises it becomes more dense until it rises above the agltatmg device and it is later discharged through the spout 3.

The amount of reduction in size of the bubbles is directly related to the extent of of the .arms and thus to the speed of the revolving arms and the duration of their action on the foam. The greater the angular velocity of the arms for a given period the smaller Wlll be the resulting bubbles and the denser the foam.

The agitating arms are suspended above the surface of the colloidized water so that the water exerts an even pressure on the rising air currents. If the agitating arms entered the water, vacuum pockets might be formed, which would tend to produce zones of less pressure on the rising currents of air and'thus air might escape entirely or varying sized bubbles might be formed.

The two sets of agitating arms travelling in opposite directions are used to minimize the effect of centrifugal force, which would tend to throw the foam outwards, leaving less depth of foam near the shaft and therefore less pressure downwards, permitting the larger bubbles to break through to the'surface near the shaft, without being sufficiently reduced in size.

The discharge opening is located several inches above the top of the agitating arms so that a layer of foam forms a matover the ascending foam and agitator, thus preVenting air from being drawn in from the atmosphere to form unduly large bubbles during the final stage of agitation. It will be-ap 1 parent that, the bubbles constantly decrease in size during the action of the agitator, thus the densitg of the foam increases In addition to acting as a mat to prevent inclusion of air from the atmosphere, this dense foam increases the downward pressure on the original large bubbles and facilitates their reduction in size under the action of the agitator.

As previously indicated the agitating arms or blades are given a stream-line.contour,

so hat vacuum pockets are not formed as the arms rotate and thus no large bubbles are permitted to form andremain unreduced in size during agitation. For example, a rotating arm having a round or square rear edge would tend to produce a vacuum pocket, in

which ascending large bubbles might be carried and thus avoid reduction in size.

It is necessary as previously stated to have the perforated plate completely covered with colloidized water, so that the air rising. through the small perforations may always be caught and held as a bubble, by a film of water. Experience has shown that the water should be kept at a constant height in order that uniform results may be obtained.

For a given size of tankorcylinder max.- imum production is achieved by having the greatest number of the smallest possible perforations in the plate 2, which with a fixed air Velocity permits relatively small bubbles to form initially, thus givin the agitator the least amountfof work to o in reducing the size of the bubbles.

It will be apparent that a foam of a required density may be readily formed by simple regulation of the operation of the process and apparatus described.

1 claim: 4

1. Apparatus for the production of foam comprising a chamber, agitating means in said chamber said agitating means comprising vertical arms, said arms having a streamline contour and means whereby said arms may be rotated, a perforated plate disposed in said chamber, -means to admit air to the mitting water to the tank above said plate said last named means comprising a ipe passing through said chamber and p ate, means for maintaining said water-at a constant level, a foam outletat the top of said tank, means disposed above said water and adapted to agitate said foam without substantially forming Whirlpools in the foam, said agitating means comprising two sets of vertical arms and means whereby said sets of vertical arms may be rotated in opposite directions.

3. Apparatus for producing foam com rising a tank, a perforated plate disposed a ove the bottom 0 said tank, defining a chamber at the bottom thereof, means for admitting air to said chamber, means for admitting water to the tank above said plate and maintaining such water at a constant level, said last named means comprising a pipe passing through said chamber and plate, a foam outlet at the top of said tank, means to agitate said foam Without substantially forming Whirlpools in the foam, said agitating means comprising two sets of vertical arms and means whereb said sets of vertical arms may be rotate in opposite directions, each arm having a stream-line contour as and for the purpose described. 5, In testimony whereof I aflix my signature.

GEORGE M. THOMSON. 

